The obstructive sleep apnea syndrome (OSAS) is an important cause of morbidity in children. Most children present with a history of snoring and difficulty breathing during sleep. However, many children presenting with these symptoms have normal sleep studies, and are diagnosed as having "primary snoring". It is not known whether primary snoring (PS) progresses to the obstructive sleep apnea syndrome. We therefore performed repeat polysomnography in a cohort of children previously diagnosed with primary snoring (PS). All children presented with symptoms suggestive of OSAS. They were diagnosed with PS if polysomnography demonstrated snoring, with less than one obstructive apnea per hour and normal gas exchange. Children were contacted 1-3 years after their initial study. Polysomnography included EEG, EOG, EMG, EKG, oronasal airflow, end-tidal PCO2, SpO2, oximeter waveform, chest and abdominal wall motion and videotaping. Nineteen children (61% female) were evaluated. Age was 6 +/- 3 [SD] yr at initial study and 7 +/-3 at follow-up. The initial apnea index was 0.1 +/- 0.2, SpO2 nadir 95+/- 2% and peak end- tidal PCO2 48 +/- 3 mm Hg. Snoring was rated as 2 +/- on a scale of0-4. Patients were restudied 1.9 +/- 0.6 years later. All were reported by their parents to still be snoring; in 11% snoring had reportedly increased, and in 67% there was no change. 78% were thought to have difficulty breathing during sleep. There were no significant changes in apnea index, SpO2,PCO2 or snoring score (0.5 +/- 0.8, 94 +/- 2% and 47 +/- 1 mm Hg, 2 +/- respectively). We conclude that primary snoring does not progress to OSA over the time span studied. Parental concern about children's breathing patterns during sleep are porr predictors of polysomnographic abnormalities.